Manufacture of useful products from mineral oils



july n, ma. W. G. LEMON www@ MANUFACTURE OF USEFUL PRODUCTS FROM MINERALOILS Filed May 1, 192e 2 sheets-sheet 1 July l, 1930. w. G. LEAMON1,769,790

MANUFACTURE OF USEFUL PRODUCTS FROM MINERAL OILS Filed May l, 1926 A2Sheets-Sheet 2 Patented July 1, 1,930

PATENT OFFICE WILLIAM G. LnAMoN, or NEWARK, onIo MANUFACTURE 0F USEFULPRODUCTS FROM MINERAL OILS Application led May 1, 1926. 4Serial No.106,072.

This invention relates to manufacture of useful products from mineraloils; and more particularly it relates to methods of and apparatus forproducing motor fuel by thermal decomposition of mineral oil materials,wherein the temperature of decomposition or cracking is controlled inaccordance with variations in rate of output of a product of the process.other than the main product sought, ywith resultant increase inaccuracy of control and general smoothness of operation.

' It has become well established renery practice to decompose oilscomposedbf large molecules for the purpose of producing therefrom oilscomposed of smaller molecules, the object usually being to produce aslarge a percentage as possible of such smaller-molecule products as areadapted for use as fuel for internal combustion engines. The fracturingor decomposing energy in all these processes is obtained b y raising thetemperature, and the processes of thus producing motor fuel have beentermed cracking processes. Determination of the optimum temperature towhich the oil should be raised in order to produce the greatestpercentage of motor fuel has been a serious practical operating problem,because the optimum tem erature for cracking one oil or mixture o oilsmay vary considerably from that of another. It has therefore been verydesirable to devise some means of automatically 'arriving at a practicaloperating temperature for any given oil and automatically maintainingsame.

This invention has to do with a process or method of, and apparatus for,automatically determining and maintaining the correct temperature forthe oil being treated in the cracking system at any given time, andautomatically varying said temperature to meet the requirements of thevarying characteristics4 of tlie oils undergoing cracking.v In allcracking systems/a zone exists, usually the zone o fmaximum temperature,in which the large-molecule oils are undergoing rapid decomposition.This zone unay be properly designated as the reaction zone of thesystem. In the process of disrupting or breaking down the largemolecules it is impossible to confine the size of all the fragmentswithin specified limits. The resultant product always consists of amixture of fragments of all sizes ranging down to and including thesmallest to which the elements of the original oil are capable of beingreduced., In fact, in any. given system at any given temperature an ap-Iproximate equilibrium is reached wherein the quantity of fragments ofone size bears a somewhat definite ratio or proportion to the quantityof fragments of another size. This makes possible in any given crackingsystem the indirect measurement of the quantity of one product of theprocess by interpretation from the direct measurement of the quantity ofanother product. Thus,l it has been found by this applicant that for agiven cracking system, measurement of the amount of fixed gases producedfrom a given quantity of originalv oil during cracking is a good indexof-the amount of motor fuel distillate produced, and 'in the practice ofthe present invention advantage is taken of this fact to achieveaccurate and most desirably automatic control of temperatures incracking operations, in a relatively simple manner.

It has been found possible, in accordance with the invention, to controlthe conditions of operation of a cracking system quite as effectively byobserving and controlling the rate of gas production as by observing andcontrolling the quantity of motor fuel distillate production.Furthermore, inasmuch as it is desirable to operate the cracking systemunder lconditions such that the yield of motor fuel distillate bears thelargest possible ratio to the amount of fixed gas produced, it has beenfound highly desirable to control the cracking temperature directly byutilizing the rate of fixed gas production to effect suchA control. Ithas also been found that the ratio of the amountof motor fuel to theamount of fixed gas produced under any given temperature conditionsvaries considerably with the cracking system employed but only slightlywith the character of the oil being cracked. Therefore, if a givencracking system be operated at such a temperature that, for a definiterate of feed of oil to be cracked, fixed gas is produced at a definiterate, a definite rate of production of oil of proper volatility for useas motor fuel will also result; and if the rate of production of fixedgas is adjusted to yield the maximum ratio of quantity of motor fueldistillate to the quantit of fixed gas for some particular type of oi,said ratio will be maintained approximately maximum over a very widerange of varying composition of original oil, assuming the rate ofproduction of fixed gas to be kept the same, although the temperaturerequired to maintain said ratio will vary widely. The ratio of fixed gasproduction to cracking stock may vary considerably, but, by way ofexample, it may be stated that good results have been obtained where theweight of fixed gases ran about 13% of the weight of cracking stockused, with a correspondin cracking temperature of 540o to 565o C. hegreat advantage of controlling the temperature of a cracking system inthis way can readily be seen from the following consideration. If thetemperature of the cracking system is lower than that required toproduce the maximum ratio of motor fuel distillate to fixed gas then theyield of motor fuel per cycle is reduced, the number of cycles requiredto attain any given result is increased, the amount of fuel and otheroperating expense is thereby increased, and the production from anygiven unit is decreased. If the temperature of the cracking system ismaintained above the temperature which gives a maximum ratio of quantityof motor fuel distillate to the quantity of fixed gas, then a portion ofthe oil that might properly be made into motor fuel is furtherdecomposed to fixed as which has a lower value to the refiner. oreoveran increased decomposition of the smaller molecules to fixed gas alsoresults in an increased quantity of fixed carbon which is highlydisadvantageous.

In the practice of the invention, therefore, the rate at which fixed gasis produced in the cracking operation is made use of, throughappropriate means, to effect regulation of the cracking operation itselfby controlling the principal variable factor involved in cracking. anoil,` namely, the temperature. The utilization of the rate of fixed gasroduction to accomplish this end may be e ected 1n various differentways, and in its broader aspects the invention is not restricted to anyparticular way.

For the sake of a concrete illustrative example by means of which theprinciples of the invention can be further explained, a typicalapparatus installation which embodies .1n practical form the principlesof the invention and by which the method of the invention can bepracticed to ood advantage will now'be described. In t e accompanyingdrawings, Fig. 1 is a more or less schematic showing of such typicalinstallation in side elevation; Fig. 2 is a similar showing but withmore details of the specific control mechanism employed; and Fig. 3illustrates details of mechanism whereby the desired temperature control1s effected in a somewhat different manner. In both Figs. 2 and 3, theshowing 0f parts of the cracking system has been simplified in somerespects.

'In the typical example here illustrated, regulation of the crackingtemperature is attained by causing the flow of the fixed gas, or aproportional part of it, leaving the condenser system, to produce adifferential pressure on mechanical actuating means which, in turn, uponsuitable variation in the pressure corresponding to change in rate offixed gas production, acts either to increase or diminish the rate ofsupply of fuel to the furnace by which the cracking zone is heated(Figs. 1 and 2), or, if the fuel supply be maintained constant, toincrease or diminish the rate at which theoil to be cracked is fed tothe cracking zone (Fig. 3) In either case the temperature in thecracking zone is thereb adjusted `as may be necessary to restore tlierate of fixed gas production to the predeterminednormal'selectedbeforehand as desirable.

The crackin system illustrated here by way of examp e only, and notbecause the invention is in any sense limited thereto, is adapted forvapor phase cracking andcomprises a pipe still heater 10, in coil 11 ofwhich mineral oil cracking stock is heated to a temperature suiicientlyhigh to vaporize a substantial part thereof and is then delivered into aseparator 12 where heavy tarry constituents drop out, the oil vaporspassing thence to a second coil 13 of the heater through which they passat highlvelocity and attain just before leaving said coil a temperaturevslightly above the cracking temperature which it is desired shallprevail in the succeeding cracking operation proper. The hot va ors thenpass into cracking chamber 14, which in this particular instance ismaintained at the desired cracking temperature by the heat contained inthe entering vapors. This chamber may desirably be filled withadsorptive contact material effective to promote the cracking reaction.Said vapors travel slowly through the chamber and undergo extensivecracking therein. The cracked vapors are then led through heat exchanger15 and fractionating column 16 where high-boiling constituents areliquefied and led thence to tank 17. The persisting vapors are led fromthe top of column 16 to a condensing and separating system 18, 19,(indicated generally at C in Figs. 2 and 3), where a liquid motor fueldistillate is recovered, part ofwhich is returned by pump 2O to the topof column 16 to serve as the reflux therefor, and the remainder gging tostorage.

The gases leaving the condensing and sep- -arating system, or a knownproportion thereof, consisting principally of fixed gas but carrying asmall percentage of very low boiling constituents recoverable ashereinafter explained but uncondensable under the conditions prevailingin the condensing and separating system aforesaid, are now caused topass through a metering appliance @,a Venturi meter in the caseillustrated, which transmits to a sensitive control device 21 throughappropriate connections 22, differential pressures in the gas line G proortional to the rate of gas flow therethroug Control device 21, whichfunctions in a manner to be presently described, has electricalactuating connections 23 to a solenoid valve R in the fuel oil line'24feeding the burners which lire the heater 10.` An auxiliary controllingdevice 25, electrically connected to said valve Rand to pyrometer v26 atthe eX- isting point of the vapors from heater coil 13, providessupplemental control means for use in starting up and controllingconditions the heater furnace.

may enter the system through line 29 and- -go to tank 17 from which itmay be drawn,

luntil the Whole system is working normally.l

4After passing through the metering appliance o, the gases may o to agasoline recovery plant 27 Where a further small quantity of low-boilinghydrocarbons utilizable as motor fuel may be liquefied, by compressionfor example, and the stripped or fixed gas may be led through line 28 tobe burned in The oil to bev cracked together with heavy condensate from15 and 16, and forced by pump 30 via line 31 through heatexchanger 15 tocoil 11 o-f the heater.A A by-pass connection 32, governed by a sole`noid-operated valve 33, affords means for cutting out'the heat exchangerwhen temperatureconditions in separator 12, as indicated by pyrometer34, render this desirable.

A To this end control device 35 is electrically connected to saidpyrometer and to valve 33,l

as shown'. A solenoid valve 36 may be provided in resi'duum line '37going from separator 12, and another, 38, in cracker stock supply line29. y These as 'Well as numerous4 other details hereinabove referred toare not essential to apparatus embodying the principles of the presentinvention and are referred to here merely for the sake of completenessin describing the particular form of apparatus here illustrated.

Returning now to the subject matter with which the invention is moreespecially concerned, and referring more particularly to Fig. 2, thedifferential pressure produced by -the flow of gas through the metering,appliance 'v is communicated to opposite sides' of a diaphragm D .Whichoperates a lever L -Which in' turn trips an electric switch S.

This switch closesor opens an electric circuit for operation of thesolenoid-valve R on the fuel line to the furnace ofthe cracking systhediaphragm moves to a position such that the switch S is closed and thevalve R is opened, thereby admitting more fuel to the furnace andbringing about an increase in temperature. The differential pressure atwhich this operation is effected is adjustable by means of thecounterweight W. When the rate of How of gas reaches an amount whichproduces a differential pressure through the Venturi tube in excess ofthe predetermined amount, the diaphragm moves in the opposite directioncausing the circuit to be broken by the sWitcl1`S and the valve R in thefuel line is closed, thereby effecting a reduction in temperature.

Another practical application, illustrated in Fig. 3, is to install thesolenoid valve R in the cracker feed line 31 to the heater coils sothat, as already stated, thereduction in temperature may be effected bypassing more cracker feed oil through the heater coils and the increasein temperature is eected by passing less.- Connecting the valve R in theby-pass 39 permits of cutting out the automatic control and adjustingthe feed man-- ually when starting up and until the system is operatingnormally.

It is to be understood, of course, that the scope of the invention isnot limited to employment of the specic types of apparatus escribed,Wide variation being possible in the form and operation of apparatusused to effectthe desired control in accordance with the principles ofthe invention. Any suitable type of flow meter may be used. Forinstance, a Pitot tube or orifice platermight be used instead of aVenturi tube. Many modiications of differential gauge could be providedand the said differential gauge might be made to operatethe valves orregulators directly instead of through an electric circuit. Theregulation of temperature might,

scribed, some other property or. characteristie of the gases, capable ofproducing an effect variable4 With the rate of gas produc' tion, vcan bemade use of in anl analogous manj ner. Thus the resistance and radiationthermometer principle, for example, could be employed for control of thedevices governing the fuel supply or oil feed supply.' The differentialpressure control has given excellent satisfaction in practice, however,and is deemed an important feature of the invenlao tion in its morespecific aspects.

What is claimed is:

1. In the conversion of mineral oil into lower-boiling products, theprocess -which comprises thermally decomposing mineral oil in a suitablereaction zone into condens- Vable products and fixed gas, condensing aliquid product from the mixture, 'obtaining from the remaininguncondensed products a quantitative indication of the rate of fixed gasproduction, and upon variation in such rate from a predeterminedVdesired normal adjusting the temperature of the reaction zone tovrestore the rate approximately to such normal.

2. In the conversion of mineral oil into lower-boiling products, theprocess which comprises cracking mineral oil ina suitable reaction zoneto produce condensable products and fixed gas, supplying cracking stockto said reaction zone at a predetermined approximately constant rate,condensing a liquid product from the vapors and gas leaving saidreaction zone, obtaining from the remaining uncondensed products aquantitative indication of the rate of fixed gas production, and, uponvariation in such rate from the normal required to maintainsubstantially constant a predetermined desired ratio between theproduction of fixed gas and the amount of cracking stock supplied tosaid reaction zone, adjusting the temperature of the reaction zone torestore the rate of gas production substantially to such normal. 3. Inthe conversion of mineral oil into lower-boiling products, the processwhich comprises cracking mineral oil in a suitable reaction zone toproduce condensable products and fixed gas, and utilizing variation inthe rate of fixed gas production to control the temperature of thereaction zone.

4. In the treatment of mineral oils to ob tain lower-boiling productstherefrom, the process which comprises heating mineral oil to crackingtemperature to evolve therefrom a mixture of condensable vapor and fixedgas, condensing a desired product from the mixture, and utilizing aquantitative measurement of the residual gas to regulate the heatingoperation and thereby to maintain the rate of production of vfixed gassubstantially at a predetermined value.

5. In the treatment of mineral oils to obtain lower-boiling productstherefrom, the process defined in claim 4, further characterized by thefact that differential pressure variations, due to change in velocity ofthe gas fiow in a given gas line, are utilized to effect the desiredcontrol.

6. In the conversion of mineral oil into lower-boiling products, theprocess which comprises cracking oil by suitable heat treatment,vcondensing a motor fuel distillate from y the cracked products, leadingaway and metering the` remaining gas, and increasing or decreasing thecracking temperature according as the metering indicates a decrease orincrease of fixed gas production with respect to a predetermined normalrate corresponding to a desired ratio between production of motor fueldistillate and production of fixed gas in said heat treatment.

7. Apparatus for thermal decomposition of mineral oil comprising, incombination, a suitably heated cracking chamber, means for regulatingthe heating of said chamber, electric circuit means arranged to actuatesaid regulating means, means for condensing and separating condensableproducts from the vapors and gases issuing from said cracking chamber, aflow meter through which fixed gas from such condensingr and separatingmeans may flow, a differential pressure gauge arranged to be affected bydifferential pressure produced by fiow of gas through said meter, switchmeans in said electric circuit means and arranged to be actuated by saidpressure gauge, upon predetermined variation in. flow of gas throughsaid meter, to close the circuit and cause operation of said regulatingmeans.

8. In an oil-cracking system, the combination, with a cracking chamber,means for controlling the temperature therein, condensing and separatingmeans into which cracked products pass from said cracking chamber, and apipe line for conducting fixed gas away from said condensing andseparating means, of a metering appliance in said line, and actuatingconnections between said metering appliance and suchtemperature-controlling means whereby the latter is automaticallyactuated to increase or decrease the temperature in said crackingchamber according as the fiow of fixed gas through said line falls belowor rises above a predetermined rate. Y 9. Apparatus for thermaldecomposition of mineral oil comprising, in combination, a convertingchamber providing a reaction zone, means for heating the saine, meansfor supplying oil to said chamber, means for sep-. arating condensatefrom fixed gas contained in the products leaving saidA chamber, meansfor measuring said fixed' gas flow, means for varying the amount of heatsupplied to said reaction zone, and means for transmitting movement ofsaid measuring means to said heat supplying means, whereby aquantitative indication is obtained of the flow `of fixed gases fromsuch separating means and the temperature in said reacting means iscontrolled by the rate of production of fixed gases.

In testimony whereof I hereunto affix my signature.

WILLIAM G. LEAMON.

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